Imported image is not showing in render
Images added to be used as "reference" or as "background" will not render, they are reference only. The same is valid for Images used as empties. Think of those images as "virtual" or "auxiliary objects" or with no renderable attributes (like a surface or material). 



If you want a plane that uses an image as a texture then you have to enable the "add images as planes" addon in the preferences window.



Now you can add an image as plane. The difference is that this addon will create real object: a plane with 4 vertices and a face that uses the image as a textures on the material. This new object is renderable.



Read also: How to map an Image on a plane manually?